John Spevacek is a chemical engineer with a confession to make. You may have noticed that snack bags are more difficult to open than they were years ago. Spevacek comes clean and takes the blame. Here's how the project came about.

I was in the Packaging Films Group, making multilayer polypropylene films for food packaging. The film had a heat-seal adhesive on one side of the polypropylene base. One of our larger clients used our films to make potato chip bags. The problem they had with our existing films was that the they seal was too weak. The client's chip-making plants were located west of the Rocky Mountains, so when trucks would drive their chips out to California, some of the seals would open up due to the pressure difference between the high altitude air and the air sealed inside the bag. And so they needed a stronger seal from us, which was then passed down to me.

So really, Spevacek is not so much to blame as the altitude of the Rocky Mountains! He goes on to describe the process of making bags and packing chips and how the new kind of seal was attained. Chip-lovers should read this, then forgive him. Link -via Gizmodo

I know someone who works for an ice-cream company and they run into the same issue. The ice-cream is whipped with air and that air expands as the product moves to higher altitudes causing the containers to overflow and lids to pop off. They only began distributing to the Rocky Mountain region recently after the opening of a new facility at a higher altitude.

The right answer is to leave enough room in the bag for expansion. That is, don't make the bag "tight" at the factory.

This is also the solution for things like plastic shampoo bottles (in your checked baggage these days). Open it, squeeze a bit and then close. Now the bottle can expand at altitude without forcing any shampoo out into your suitcase !